Question

If .00327 g of a gas dissolves in 0.376 L of water at 867 torr, what quantity of this gas (in grams) will dissolve at 759 torr?

Answer 1

At 759 torr, 0.002 86 g of the gas will dissolve.

Henry’s law states:

$c = k_{H}p$, where

where $K_{H}$ is a proportionality constant called the Henry's Law constant.

If we have the same solute in the same solvent at two different pressures  $p_{1}$ and $p_{2}$,  

$c_{1} = k_{H}p_{1}$ and $c_{2} = k_{H}p_{2}$

Dividing the two equations, k_H cancels and we get

c_1/c_2 = p_1/p_2

c_2 = c_1 × p_2/p_1

The volumes of solvent are the same, so we can use the masses of the solute instead of concentrations.

∴ c_2 = 0.003 27 g × (759 torr/867 torr) = 0.002 86 g